How does power flow through a high-voltage AC transmission line in a steady state, where the voltage remains nearly constant along the line? Or how is power transferred from a generator to a load in a networked Bulk Electric System (BES)?
Understanding power flow can become complex quickly, but the key factor is that power mainly flows when there’s a difference in the phase angle between the sending and receiving buses. To break it down to basic principles, real power flow is governed by the following equation:
Maximum power transfer occurs when the phase angle difference between the sending and receiving buses is 90 degrees, which is referred to as the steady-state stability limit (SSSL).
Phase angle differences vary with changes in loading and generation, and they can also be intentionally adjusted using phase-shifting transformers.